Control of current to large inductances.



J. C. SMITH.

CONTROL OF CURRENT TO LARGE INDUCTANCES,

APPLICATION FILED OCT. 14. 1912. 1,216,867. Patented Feb. 20,1917.

3 SHEETS-SHEET I.

17 m W I INVENTOR.

J. C. SMITH.

CONTROL OF CURRENT TO LARGE INDUCTANCES.

APPLICATION mm M114. 1912.

1 ,21 6,867. Patented Feb. 20, 1917.

3 SHEETS-SHEET 2 l V/TNESSES [1V V E N TOR 1/ fmt J. C. SMITH.

CONTROL OF CURRENT T0 LARGE INDUCTANCES.

APPLICATION FILED OCT. 14. I912.

1,216,867. Patented F61). 1917,

3 SHEETS- 3.

,. f m1 k M WlITNESSES: INVENTOR.

PATENT OFFICE.

JOHN C. SMITH, OF LOUISVILLE, KENTUCKY.

CONTROL OF CURRENT TO LARGE INDUCTANCES.

Specification of Letters Patent.

Patented Feb. 20, 1917.

Application filed October 14, 1912. Serial No. 725,652.

To all whom it may concern:

Be it known that 1, JOHN C. SMrrH, a citizen of the United States, residing in Louisville, in the county of Jefferson and State of Kentucky, have invented new and useful Improvements in Control of (lurrent to Large Inductances, of which the following is a specification.

My invention relates to the control of current to large inductances, and has for an object the prevention of sparking at switch contacts.

lVhen current is cut off from an inductance, an induced current of high voltage, but low amperage, flows momentarily in the same direction to the line current, this induced current is of a disruptive nature and very destructive to switch contacts. Many methods have been tried to prevent or minimize the are formed by the induced current, such as separating the terminals in a nonconducting fluid, such as oil; and by separating them in a magnetic field, the lines of magnetic force serving to blow the are out. These methods while more or less successful are cumbersome.

My invention reduces the sparking at terminals to a minimum by means of the arrangement. of apparatus and circuits set forth hereinafter, set forth in the appended claims, and illustrated in the accompanying drawings that form a part of this specification, and in which like parts are designated by similar reference characters in the several views.

In the drawings Figure 1, is a diagrammatic plan, or wiring diagram, showing an embodiment of my invention as applied to the shunt field of a motor, with its circuits and switches, as used in a system of elevator control, showing the different parts in the positions wherein they stand when the motor is at rest. Fig. 2, is a view similar to Fig. 1 but showing the position assumed by the parts when the car switch has been moved, partly over, to run the elevator up. Fig. 3 diagrammatically illustrates the method of connection.

Referring to the drawings, and, more particularly Figs. 1 and 2, wherein is shown an embodiment of my invention as applied to a motor used in elevator service, A indicates a main potential switch, B an accelerating switch, -C a dynamic resistance switch, F- a speeding-up switch, -G a reversing switch, --H a wall switch, I a compound wound motor, J an auto-limit switch, K a manually operated car switch, -L a slaclecable switch, -M a brake magnet, -N a slow-down switch, 0 and P upper limit switches. These devices are all well known in the art and need no description, as any desired construction may be used. though preferably I have illustrated A, B, C, F, G, J, and K as being the same as those shown and described in my copending application #636,825, filed July 5, 1911. The car switch K is of the class in which a contactor is adapted to be brought into contact with a series of contacts when shifted in either direction from a central position. Current be.- ing given thereto from the wall switch H by lines 2 and 2, slack-cable switch L and line 8. Moving the switch K to the right (the up direction) will bring elevation 10-2- into contact with contact -i11 giving current to the reversing switch G, the circuit being by line -9 to and through the solenoid 301 thence by line -10 to auto-limit switch J, thence by lines -11 and 3 to the wall switch H, this will set the reversing switch and pilot switch levers -312 and 316 in the position shown in Fig. 2. The shifting of the lever 316 gives current to the solenoid E of a subswitch E, the circuit being from the switch H by lines 2 and 12 to, and through, E thence by line 13 to contact -318- through lever -316 and line -l4+ to switch H. The switch E may be of any suitable construction, the one here illustrated being of the plunger type in which contactors are insulatedly attached to a plunger .and adapted to be brought into contact with contact fingers by the attraction of the plunger within the solenoid. The attraction of the plunger within the solenoid will close contacts E, E open contacts E, E and close contacts E, E, in the sequence named. It is to be observed that a circuit parallel with the. shunt field extends from line 5 by way of line 15, contactor E contacts E and E and line 4 to switch H, the circuit to the shunt field being by line 5 to motor terminal f, through the shunt field thence by line 3 to switch H. On closing contacts E E, by contactor E, current flows from line 2 by way of line 6, resistance SR to contact E" here the current divides, one portion going, by the circuit just de- ..scribed, through the shunt field to switch H,

the other going by the parallel circuit to switch H. Just after the contactor E closes on contacts E E contactor E opens contacts E EZbreaking the parallel circuit and allowing the full current to go to the shunt field.

. It will be observed that this excites the field while current has not yet been given to the armature, it is also to be observed.

that contacts E- B are in the operating circuit of the mainv potential=switch A, that gives current to the armature, hence the main switch can not be operated until E has completed its movement. This arrangement assures the excitation of the field previous to the giving of current to the armature. Further movement of the car switch K will bring elevation 403 into contact with 405 this will give current to the solenoid of the main potential switch A, the circuit being by line 16 to and through the auto limit switch J thence by line 17 to upper limit switch 0 thence to and through a locking coil on the solenoid 301, through pilot switch lever 312, thence by line 20 to and through contacts 10 -12 thence by line 21 to and through the solenoid 101, of switch A, thence to and through the pilot switch lever 211, by lines 23-24 and 2- to switch H, this closes the main switch. Current is given to one side of the main switch by line 2 to contact 106, and by lever 104 to points 108-110; and from points 109-111 through lever 105 to contact l07 thence by line 2- to the wall switch H. Closing of the main switch gives current to the brake magnet from point 108 by line 25 to and through the brake-magnet thence by line 24 and 2- to switch H. Closing of the main switch gives current to the shunt field, of the motor, from point 110 by line 49 to and through the speedinghp switch F, by line 50 to line 6 through contacts hi -E by line 5 to motor terminal f, thus shunting the resistance SR and giving full line current to the shunt field. l'Vith the closing ofswitch A current is given to the series field and armature from point 110 by lines 26-27 to and through the resistance coils 27-'-27" and 27", by lines 28-29 to motor terminal 0 through series field 6l to terminal 0', by line 30 to 306 on reversing switch G through 310, by line 31 to motor terminal a", by line to and through 308-307 to 305, on reversing switch, 33 to point 111 on main switch A. This starts the motor up at slow speed. A further movement of the car switch will bring elevation 404 into contact with 408 giving current to the accelerating switch B, by line 34 to and through the auto limit switch J, by line 35 to and through the operating coil 201, thence'by line 36 to and through pilot switch lever 315, by hnes 37-33 to point 101 on switch A. This starts the accelerating switch, the accelerating switch illustrated is of the class in which a plurality of members operates seriatz'm to cut resistances in and out of circuit, the first and last members being adapted to shift pilot levers. The movement of the first member, 204, of the accelerating switch shifts lever 211 bringing it into contact with point 214, this energizes the dynamic switch C, the circuit being from line 2 by 38 to and through the coil of C, by .39 to point 214 through lever 211, by 23-24 to 2-. The energization of C opens a dynamic resistance circuit, that may be traced as follows, from the motor terminal a by lines 32-40 to point C through lever C line 41, resistance 42, lines 43-31 to motor terminal a. .This circuit is not open until the accelerating switch starts. Members 203-204 and 205, of the accelerating switch, contact successively with points 207-208 and 209 cutting out coils 27'-27" and 27' from the Series field and armature circuit; member 206 contacts with 210 cutting out the series field, the armature circuit then being from point 110, on the main switch, by line 26 to and through the accelerating switch to point 210 thence by lines 44-30 to 306 on the reversing switch, through 310, by 31 to motor terminal a through armature 62 to terminal a, by 32 to the reversing switch thence by 33 to point 111 on the main switch. As the first member, 203, of the accelerating switch moves it shifts the lever 211 breaking the operating circuit of the main switch at 213, this would allow the main switch to drop out, but that in closing the main switch had closed a holding circuit through resistance 45 to point 109. As the last member of the accelerating switch raises it shifts the pilot lever 215 breaking contact at 217 and mak ing it at 218. Breaking contact at 217 inserts resistance 219 in the operating circuit of solenoids 201; closing the contact 218 gives current to one side of the speeding-up switch F by line 46; current being given to the other side by a further movement oi? car switch K bringing elevation 402 into con tact with 410, the circuit being by line 47 to contact IN. on the slow-down switch N, through lever N ,by line 48 to F. The energization of F opens the shunt field circuit, from the main switch, at F inserting resistance RS in the shunt field circuit weakening the same and, speeding up the motor. To bring the motor' to rest the switch K is returned to a central position, the various switches acting in sequence and manner reverse to that set forth. The switch F cutting the resistance SR out of the shunt field circuit, the accelerating switch as it falls out cutting in the series field and the resistances 27 -27 and 27 into the armature circuit, as the last member falls out'it opens the operating circuit of switch C and this closes the dynamic bra-king circuit across the armature terminals. The main potential switch A in falling out opens u only the armature circuit as the shunt eld is held open by the sub-switch E. The shunt field remaining excited allows full advantage to be had of the dynamic resistance caused by the surge of induced current in the armature circuit. The sub-switch E is the last to fall out, and in so doing cuts resistance SR out by opening the contacts EE and by closing contacts EL -E circuits the shunt field on itself. As the armature and shunt field completes the circuit that is parallel with the shunt field, as this circuit is in connection with line 5 to, and line 3 from, the shunt field it provides a path for currents induced in the shunt field. At no time is the circuit through the shunt field opened, it is only shunted, and the current induced therein will be very light owing to the line current being cut down by the resistance SR. As the armature and shunt fields are both provided with closed circuits around which the induced currents may surge, it is evident that there will be no sparking at switch terminals.

In Fig. 5, is illustrated, diagrammatically the several steps in my method of control. At IV the line is open at E and the circuit parallel with the inductance closed at E At X the line is closed at E current going to the inductance parallel circuit through the resistance SR, E being still closed. At Y, the parallel circuit has been open at E and current is flowing through the resistance to the inductance. At Z E has been closed shunting the resistance SR giving full line current to the inductance. In cutting off current from the inductance these actions occur in the reverse order to that just stated.

Other methods of adapting my invention to various conditions of service will suggest themselves to those skilled in the art, and it is to be understood that I do not limit myself to the instances illustrated.

Having described my invention so that any one skilled'in the art pertaining thereto may make and use the same, I claim 1. The method of controlling current to an inductance, Comprising a closed circuit across the terminals of the inductance, the admission of current thereto through a resistance while said circuit is closed, opening the closed circuit and then short-circuiting the resistance.

2. The method of controlling current to an inductance by inserting a resistance in the circuit thereto, closing a circuit across the terminals thereof and then cutting off current thereto.

3. In combination with an inductance, and a source of electric current therefor, a normally closed circuit across the terminals of the inductance, means for giving current to said inductance through a resistance, and means for opening said closed circuit and short circuiting said resistance.

4. In combination with an inductance, and a source of electric current therefor, an initially closed circuit across the terminals of the inductance, means for giving current to the inductance with said closed circuit in parallel therewith, and means for short cir, cuiting the resistance.

5. In combination with an inductance, and a. source of current therefor, means for inserting a resistance in the circuit thereto closing a circuit across the terminals thereof, and then opening the line circuit.

6. In combination with an inductance and a source of current therefor, a circuit in parallel with said inductance, means for giving current through a resistance to said inductance and parallel circuit and means for opening said circuit and short circuiting the resistance.

7. An inductance, a switch for-controlling the direction of current therethrough, a circuit in parallel with said inductance, a resistance, an electro-magnetic switch adapted to give current through said resistance to the inductance and the parallel circuit, said electromagnetic switch controlled by said first named switch.

normally closing said circuit and adapted'to give current through said resistance to said inductance and parallel circuit and subsequently open the parallel circuit, and means for controlling said electro-magnetic switch.

9. An inductance, a main switch, a subswitch, means for operating same, a resistance, a circuit in parallel with said inductance and normally closed by said subswitch, said sub-switch being adapted to give current through said resistance to the inductance and the parallel circuit, and later to open said parallel circuit, said main switch adapted afterthe operation of the sub-switch to give'current direct to the inductance thereby short circuiting said resistance.

JOHN C. SMITH. Witnesses:

M. J. RoBER'rsoN, W. B. MUNNELL. 

